A Potential Outcomes Approach to Estimating Cases of Invasive Pneumococcal Disease Prevented After the Introduction of a New Pneumococcal Vaccine

• Activity Number: 492
• Type: Contributed
• Date/Time: Wednesday, August 7, 2013 : 8:30 AM to 10:20 AM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Tracy Pondo*+ and Elizabeth R Zell and Matt Moore and Thomas H Taylor
• Companies: Centers for Disease Control and Prevention and Centers for Disease Control and Prevention and Centers for Disease Control and Prevention and Centers for Disease Control and Prevention
• Keywords: potential outcomes ; PCV13 ; vaccination

Abstract

In 2010, a new vaccine, PCV13, was introduced for the prevention of invasive pneumococcal disease (IPD) caused by the bacterium Streptococcus pneumoniae. We used a potential outcomes approach to estimate the cases of IPD prevented in children less than 2 years old after PCV13 vaccine introduction. With data from an active, population-based surveillance system, we modeled the monthly IPD case counts for children less than 2 years old between 2005 and 2010 to generate a set of parameter estimates and their variance-covariance matrix. Assuming that the parameter estimates followed a normal distribution, we drew 1000 sets of randomly varying parameter estimates. We then imputed predicted monthly case counts occurring between July 2010 and June 2012. To estimate the percent change from baseline and a range of cases prevented by PCV13, we compared the predicted cases of IPD in the absence of PCV13 to the actual number of cases observed after PCV13 introduction. This approach to estimating the public health impact of PCV13 will be used to inform national vaccination policy.